principal tributary of the Benue River, northeastern Nigeria. It rises in several branches (including the Lere and Maijuju rivers) on the eastern slopes of the Jos Plateau and cascades (with several scenic waterfalls) onto the plains of the Gongola Basin,...

river in southwestern Tasmania, Australia. The Gordon River rises from Lake Richmond in the King William Range of the central highlands and flows southeast around a great bend to the southwest and finally northwest to enter the Indian Ocean at Macquarie...

river that, together with the Campaspe and Loddon rivers, drains most of central Victoria, Australia. Rising on Mount Singleton in the Eastern Highlands northeast of Melbourne in Fraser National Park, the Goulburn flows generally north for 352 miles...

river rising near Creston, Union county, south-central Iowa, U.S., and flowing in a southerly direction into Missouri. It merges with the Thompson River and Shoal, Medicine, and Locust creeks near Chillicothe, Mo., before joining the Missouri River near...

river, south-central Brazil. It rises in the Mantiqueira Mountains almost in sight of Rio de Janeiro city and descends inland, west-northwestward, in many falls and rapids. Its lower course marks a portion of the Minas Gerais–São Paulo border. At the...

river in the Cape Midlands, Eastern Cape province, southern South Africa. The Great Fish River has a length of 430 miles (692 km) and a drainage area of 11,900 square miles (30,800 square km). Its main northern tributary, the Great Brak River, rises...

river in western Africa, rising 25 miles (40 km) north of Kindia in the Fouta Djallon highlands of western Guinea. It marks 63 miles (101 km) of the Guinea–Sierra Leone border before entering Sierra Leone to complete its 160-mile (257-kilometre) course...

river rising near Kings Mountain in Lincoln county, central Kentucky, U.S., and flowing for 360 miles (580 km) generally westward through a well-defined gorge, then northwestward to the Ohio River, which it enters just above Evansville, Ind. Dams and...

river in the western United States, rising on the Continental Divide in the Wind River Range in west-central Wyoming. It flows generally south through southwestern Wyoming, where it is dammed below La Barge to form the Fontenelle Reservoir. Below Green...

river in southeastern Mexico. Its headstreams, the largest of which is the Cuilco, rise in the Sierra Madre of Guatemala and the Sierra de Soconusco of Mexico. The Grijalva flows generally northwestward through Chiapas state, where it is known locally...

natural or artificial cave used as a decorative feature in 18th-century European gardens. Grottoes derived from natural caves were regarded in antiquity as dwelling places of divinities. Grottoes were often constructed from a fanciful arrangement of...

major watercourse of southern Spain. Rising in the mountains of Jaén province, it flows in a generally westward direction for 408 miles (657 km), emptying into the Atlantic Ocean at Sanlúcar de Barrameda, on the Gulf of Cádiz. It drains an area of 22,318...

one of the longest streams of the Iberian Peninsula, flowing generally westward through south-central Spain and southeastern Portugal to the Gulf of Cádiz in the Atlantic Ocean. The river has a drainage area of 23,455 square miles (60,748 square km),...

river flowing through west central Brazil. The river rises in the Serra (mountains) dos Parecis in Mato Grosso state, Brazil, and loops southward, westward, and then north-northwestward past Mato Grosso city. After receiving the Rio Verde, it continues...

river system of the coastal lowlands of Ecuador. Its eastern tributaries rise on the western slopes of the Andes and descend to drain the wet lowlands. Official usage as to how much of the system should be called the Guayas River differs; the name is...

northern tributary of the Xi River, southern China. Its upper course is also called the Li River. The Gui River rises in the Mao’er Mountains to the north of Guilin in the northern part of the Zhuang Autonomous Region of Guangxi and flows southward to...

any large coastal indentation. More specifically, such a feature is the reentrant of an ocean, regardless of size, depth, configuration, and geologic structure. The nomenclature for gulfs is far from uniform; names that may refer to sizable gulfs in...

river that rises in eastern Afghanistan near Sarwāndī on the Khumbur Khūlē Range and enters western Pakistan near Domandi, being joined there by the Kundar River. Further joined by the Wāna Toi and Zhob rivers, it falls into the Indus River just south...

British diplomat and archaeologist who was the husband of Emma, Lady Hamilton, the mistress of Admiral Horatio Nelson. Hamilton was the son of Lord Archibald Hamilton, governor of Jamaica. He served in the army (1747–58) but left it after his marriage...

river, northern South Korea, rising in the western slopes of the T’aebaek-sanmaek (mountains) and flowing generally westward across the peninsula through the provinces of Kangwŏn, Kyŏnggi, and North Ch’ungch’ŏng and through the city of Seoul to the Yellow...

river in eastern Guangdong province, China. The Han River rises in the Wuyi Mountains in southwest Fujian province to the north of Changting. Its upper course is known as the Ting River, and it flows south to Fengshi, below which it is joined by the...

one of the most important tributaries of the Yangtze River (Chang Jiang) of China. It has a total length of about 950 miles (1,530 km). The Han River rises in the Shenqiong Mountains, part of the Micang Mountains in the extreme southwestern part of Shaanxi...

river, Central Asia. It rises on the western slopes of the rugged Selseleh-ye Kūh-e Bābā range, an outlier of the Hindu Kush mountains, in central Afghanistan. Flowing west past Chaghcharān and the ancient city of Herāt (whence its name is derived),...

tributary of the Elbe River in Germany. It rises on the Mecklenburg Plateau 7 miles (11 km) northwest of Neustrelitz and flows through the Mecklenburg lakes before heading south as far as Spandau (in Berlin), where it is joined by the Spree River. Curving...

river rising in the Great Dividing Range north of Lake George, New South Wales, Australia, and flowing 293 miles (472 km) north and east to the Tasman Sea at Broken Bay. It drains an area of about 8,390 square miles (21,730 square km). Known as the Wollondilly...

river rising in central Gansu province, China, and flowing into the western Alxa Plateau (Ala Shan Desert) in western Inner Mongolia Autonomous Region. The river is formed by a series of small glacier-fed rivers flowing north from the Nan and Qilian...

river in southwestern Afghanistan and eastern Iran, about 715 miles (1,150 km) long. Rising in the Bābā Range in east-central Afghanistan, it flows southwestward across more than half the length of Afghanistan before flowing northward for a short distance...

river in northeastern Queensland, Australia. The river rises in the Eastern Highlands, flows for 150 miles (240 km) southeast across the Atherton Plateau past Ingham, and enters the Coral Sea at Halifax Bay in the Hinchinbrook Channel. A relatively deep...

river rising in the Blue Ridge Mountains, Towns county, northern Georgia, U.S. It flows north into North Carolina past Hayesville, northwest past Murphy, into southeastern Tennessee, where it joins the Tennessee River 31 miles (50 km) northeast of Chattanooga...

river in Guizhou province and in the Zhuang Autonomous Region of Guangxi, southwestern China. It is one of the principal tributaries of the Xi River, which forms its delta at Guangzhou (Canton). The Hongshui River rises on Mount Maxiong in Qujing, Yunnan...

spring with water at temperatures substantially higher than the air temperature of the surrounding region. Most hot springs discharge groundwater that is heated by shallow intrusions of magma (molten rock) in volcanic areas. Some thermal springs, however,...

river in southwestern New England, rising in the Berkshire Hills, near Pittsfield, Mass., U.S. It flows southward for 148 miles (238 km) through Massachusetts past Pittsfield, Lee, and Great Barrington; and then through Connecticut past New Milford,...

river in east-central China that drains the plain between the Huang He (Yellow River) and the Yangtze River (Chang Jiang). The river has a length of 660 miles (1,100 km) and drains an area of 67,000 square miles (174,000 square km). It is fed by numerous...

principal river of northern China, often called the cradle of Chinese civilization. It is the country’s second longest river, with a length of 3,395 miles (5,464 km), and its drainage basin is the third largest in China—an area of some 290,000 square...

river in New York state, U.S. It flows almost entirely within the state, the exception being its final segment, where it forms the boundary between New York and New Jersey for 21 miles (34 km). The Hudson originates in several small postglacial lakes...

river in West Bengal state, northeastern India. An arm of the Ganges (Ganga) River, it provides access to Kolkata (Calcutta) from the Bay of Bengal. It is formed by the junction of the Bhagirathi and Jalangi rivers at Nabadwip. From there the Hugli flows...

river on the western side of the island of Newfoundland, Can., rising in the Long Range Mountains, inland from St. Pauls Inlet. It flows generally southward for 75 miles (121 km) over a series of falls and through several lakes, including Deer Lake,...

river formed by the confluence of the East and North forks, Elko county, north-central Nevada, U.S. The headwaters of the Humboldt rise in the Ruby, Jarbidge, Independence, and East Humboldt mountain ranges in Humboldt National Forest. Flowing in a tortuous...

river in east-central New South Wales, Australia, rising in the Mount Royal Range of the Eastern Highlands and flowing generally southwest through Glenbawn Reservoir (for flood mitigation and irrigation) and past Muswellbrook and Denman. There, joined...

river in northern Zimbabwe and Mozambique, rising northwest of Marondera (formerly Marandellas) and flowing westward past Harare (formerly Salisbury) to Kutama. The river then turns north past Chinhoyi (formerly Sinoia) and the Hunyani Range and cuts...

river in southern Tasmania, Australia, rising on the slopes of Mounts Wedge, Bowen, and Anne. It flows south and then, blocked by the Arthur Range, east to be joined by its tributaries, the Weld and Picton rivers, below Huon Gorge. Turning southeast,...

English-born American zoologist known for his ecological studies of freshwater lakes. Hutchinson was educated at Greshams School in Holt, Norfolk, and at the University of Cambridge. He lectured for two years at the University of the Witwatersrand in...

river in southern North Island, New Zealand. It rises in the Tararua Range and, fed by the Pakuratahi, Mangaroa, Akatarawa, and Whakatikei rivers, flows south to enter Wellington Harbour after a course of 35 miles (56 km). It supplies much of the fresh...

cavity in ice or an underground cave that has permanent ice deposits. The two types of ice cave are wholly unrelated. The first type of ice cave is formed by meltwater streams carving labyrinths in the bases of glaciers or by streams and wind hollowing...

river flowing through Santa Catarina and Paraná states in southern Brazil. The Iguaçu is formed by headstreams rising in the Serra do Mar near Curitiba. It winds generally westward through the uplands for about 820 miles (1,320 km) before joining the...

river in western Uygur Autonomous Region of Xinjiang, China, and southeastern Kazakhstan. It is 870 miles (1,400 km) long and drains the basin between the Tien Shan range to the south and the Borohoro (Poluokenu) Mountains to the north. Both ranges are...

navigable stream of northern and central Illinois, U.S. It is formed by the junction of the Des Plaines and Kankakee rivers in Grundy county, about 10 miles (16 km) southwest of Joliet. It flows generally west across the state until just north of Hennepin,...

body of salt water covering approximately one-fifth of the total ocean area of the world. It is the smallest, youngest, and physically most complex of the world’s three major oceans. It stretches for more than 6,200 miles (10,000 km) between the southern...

river, Sakha republic (Yakutia), far eastern Russia. It is one of the major rivers of northeastern Siberia. The Indigirka rises in the Verkhoyansk Mountains and flows 1,072 miles (1,726 km) north through the Chersky Range into the broad Indigirka lowland,...

river, west-central France, a left-bank tributary of the Loire River. Rising on the northern flanks of the Massif Central, it flows 165 miles (265 km) northwestward through Indre and Indre-et-Loire départements, joining the Loire northwest of Chinon...

great trans- Himalayan river of South Asia. It is one of the longest rivers in the world, with a length of some 2,000 miles (3,200 km). Its total drainage area is about 450,000 square miles (1,165,000 square km), of which 175,000 square miles (453,000...

a major right- (south-) bank tributary of the Danube River. The Inn River is 317 miles (510 km) long. It rises in Lake Lughino in Switzerland and flows northeast across western Austria and southern Germany. The river’s Swiss section is called the Engadin....

river, west-central Alaska, U.S. It is the westernmost major tributary of the Yukon River. The Innoko rises in the Kuskokwim Mountains west of the town of McGrath and flows north and then southwest for about 500 miles (800 km) before joining the Yukon...

river flowing through the centre of Iowa, U.S. It rises as two headstreams, the East Branch Iowa and West Branch Iowa rivers, in the north-central part of the state; the Iowa proper is formed by their confluence near Belmond in Wright county. The river...

principal river of Myanmar (formerly Burma), running through the centre of the country. Myanmar’s most important commercial waterway, it is about 1,350 miles (2,170 km) long. Its name is believed to derive from the Sanskrit term airāvatī, meaning “elephant...

major river of west-central and western Asia. With a length of 2,640 miles (4,248 km), it is one of the continent’s longest rivers. The Irtysh and the Ob River, of which the Irtysh is the principal tributary, together constitute the world’s seventh longest...

river, Bavaria Land (state), southern Germany. Rising at an elevation of 5,741 feet (1,750 m) in the Karwendelgebirge, just northeast of Innsbruck, Austria, the Isar runs west and then north crossing into Germany at Scharnitz Pass. The river there flows...

river, southeastern France, originating in the Savoy Alps on the Italian frontier and flowing 180 miles (290 km) to its confluence with the Rhône above Valence, draining a basin of approximately 4,600 square miles (12,000 square km). It rises in an amphitheatre...

river in northern and western Hokkaido, northern Japan, the third longest in the country. It rises near the centre of the Kitami Mountains and flows for about 167 miles (268 km) southwest in a broad arc, draining the Kamikawa Basin, the Sorachi River...

river in northern Kazakhstan and Tyumen and Omsk oblasti (provinces) of south-central Russia. A left-bank tributary of the Irtysh (Ertis) River, it rises in the Niyaz Hills in the north of the Kazakh Uplands (Saryarqa), flows west through Astana, and...

longest (after the Danube) river in Bulgaria, formed south of Samokov in the Rila Mountains by its headstreams, the Beli (White) Iskŭr and Cherni (Black) Iskŭr. It cuts a 40-mile (65-km) gorge through the Balkan Mountains to bring the high basin of Sofia...

any area of land smaller than a continent and entirely surrounded by water. Islands may occur in oceans, seas, lakes, or rivers. A group of islands is called an archipelago. Islands may be classified as either continental or oceanic. Oceanic islands...

river, Rio Grande do Sul estado (“state”), southern Brazil. It rises in the hills east of Passo Fundo and flows southward and eastward for 280 miles (450 km), receiving the Taquari, Caí, Sinos, and Gravataí rivers near its mouth. There, at Porto Alegre,...

river, Ceará estado (“state”), northeastern Brazil. It is formed by the junction of the Carapateiro and Trici rivers (originating in the Serra Grande) and flows northeastward for approximately 350 miles (560 km) to enter the Atlantic Ocean east of Maceió...

river in central Virginia, U.S., formed by the junction of the Jackson and Cowpasture rivers and cutting across the Great Appalachian Valley in northern Botetourt county. It flows in an easterly direction, crossing the Blue Ridge Mountains through a...

island country lying off the east coast of Asia. It consists of a great string of islands in a northeast-southwest arc that stretches for approximately 1,500 miles (2,400 km) through the western North Pacific Ocean. Nearly the entire land area is taken...

river, northern Brazil, rising on the southern slopes of the Tumuc-Humac Mountains and flowing in a generally southeasterly direction for about 350 miles (560 km) to join the Amazon River at Bôca do Jari, opposite Grande de Gurupá Island. The Jari forms...

French biologist best remembered for his work on the subterranean coleopterans of the family Anisotomidae. His exploration of the caves of the Pyrenees and Carpathian mountains yielded many species of these small, shiny, round fungus beetles that were...

river, most westerly of the Missouri River ’s three headstreams, rising in the Gravelly Range in southwestern Montana, U.S., near the Continental Divide and Yellowstone National Park (where it is known as Red Rock River). It flows west through Red Rock...

American civil engineer who made outstanding contributions in the construction of U.S. canals, railroads, and water-supply systems. Jervis worked as an axman on the survey for the Erie Canal and earned rapid promotion on that project thereafter, serving...

river, westernmost of the five rivers in the Punjab that merge with the Indus River in Pakistan. The Jhelum rises from a deep spring at Vernag, in Jammu and Kashmir state, in the Indian -administered portion of the Kashmir region. The river meanders...

river in central China. A tributary of the Yangtze River (Chang Jiang), with the largest drainage area of the Yangtze basin, it rises in the rugged western outliers of the Qin (Tsinling) Mountains in southern Gansu province. It flows south and east into...

westernmost of the major headwater streams of the Yangtze River (Chang Jiang), southwestern China. Its headwaters rise in the Wulan and Kekexili (Hoh Xil) ranges in western Qinghai province, to the south of the Kunlun Mountains, and on the northern slope...

river in southeastern Fujian province, China. The river rises in the mountains northwest of Zhangzhou, draining a large interior basin above Zhangping. The Xinqiao River and the Yanshi River and their tributaries drain the northeast and the southwest...

river with the lowest elevation in the world. It rises on the slopes of Mount Hermon, on the Syrian-Lebanese border, flows southward through northern Israel to the Sea of Galilee, and then divides Israel and the Israeli-occupied West Bank on the west...

principal river of Somalia in northeastern Africa. Originating via its headwater streams in the Mendebo Mountains of southern Ethiopia, it flows about 545 miles (875 km) from Doolow on the Ethiopian frontier to the Indian Ocean just north of Kismaayo,...

river in eastern Spain, rising in the Universales Mountains north of Cuenca city. It flows in a southerly and then easterly direction for 309 miles (498 km) through Cuenca, Albacete, and Valencia provinces and into the Gulf of Valencia, at Cullera. Beyond...

river that rises in the highlands east of the Ucayali River in east-central Peru. It flows northward through Acre state, Brazil. Entering Amazonas state, Brazil, it meanders eastward and then east-northeastward, emptying into the stretch of the Amazon...

river in eastern Afghanistan and northwestern Pakistan, 435 miles (700 km) long, of which 350 miles (560 km) are in Afghanistan. Rising in the Sanglākh Range 45 miles (72 km) west of Kabul city, it flows east past Kabul and Jalālābād, north of the Khyber...

main tributary of the Niger River, in central Nigeria. It rises on the Jos Plateau 18 miles (29 km) southwest of Jos town near Vom and flows in a northwesterly direction to a bend 22 miles (35 km) northeast of Kaduna town. It then adopts a southwesterly...

river in Zambia, rising near the country’s border with the Democratic Republic of the Congo. It meanders generally southward until it turns west near the Lukanga Swamp (which it drains). The river then flows south and finally east through the Kafue Flats...

most remote headstream of the Nile River and largest tributary of Lake Victoria, rising in Burundi near the northern tip of Lake Tanganyika. It is formed at the confluence of its two headstreams—the Nyawarongo (Niavarongo) and the Ruvubu (Ruvuvu)—which...

river, west-central Lebanon, flowing westward and emptying into the Mediterranean Sea north of Beirut. Apart from a small section near the coast the river is seasonal; in summer its only source is a spring at the Jʿītā Cave. The river is about 19 miles...

river in west-central Russia. Rising in the Upper Kama Upland of Udmurtia, it flows north, then east, south, and southwest for 1,122 miles (1,805 km) until it enters the Volga River below Kazan, in the Samara Reservoir. It drains a basin of 202,000 square...

river formed at Gauley Bridge, West Virginia, U.S., by the confluence of the New and Gauley rivers. It flows 97 miles (156 km) in a northwesterly direction to enter the Ohio River at Point Pleasant. It is navigable via dams and locks to Kanawha Falls,...

stream in northeastern Kansas, U.S. It is formed by the confluence of the Republican and Smoky Hill rivers at Junction City and is joined by the Big Blue River near Manhattan. Flowing east into the Missouri River at Kansas City for a distance of about...

river in southwestern Iran, a tributary of the Shatt al-Arab, which it joins at Khorramshahr. It rises in the Bakhtīārī Mountains west of Eṣfahān and follows a tortuous course trending basically southwest. The Kārūn’s total length is 515 miles (829 km),...

river in central Africa. It is the chief southern tributary of the Congo River, into which, at Kwamouth, Congo (Kinshasa), 125 miles (200 km) above Malebo (Stanley) Pool, it empties a volume approaching one-fifth that of the main stream. The longest...

partly navigable stream in central and southern Illinois, U.S. It rises in Champaign county near Urbana and flows southwest to enter the Mississippi River north of Chester, in Randolph county, after a course of 320 miles (515 km). About 50 miles (80...

sacred river of southern India. It rises on Brahmagiri Hill of the Western Ghats in southwestern Karnataka state, flows in a southeasterly direction for 475 miles (765 km) through the states of Karnataka and Tamil Nadu, and descends the Eastern Ghats...

river in west-central Maine, U.S. The Kennebec rises from Moosehead Lake and flows south for about 150 miles (240 km) to the Atlantic Ocean. It was explored by Samuel de Champlain between 1604 and 1605. Fort St. George, founded in 1607 at the head of...

tributary of the Ohio River in north-central Kentucky, U.S., and navigable along its 259-mile (417-km) course by means of locks. It is formed by the confluence of North, Middle, and South forks near Beattyville in Lee county and empties into the Ohio...

river, an important tributary of the Euphrates River. It rises in the mountains of southeastern Turkey near Diyarbakır and flows southeastward to Al-Ḥasakah, Syria, where it receives its main tributary, the Jaghjagh; it then meanders south to join the...

tributary of the Mae Klong River, flowing wholly in western Thailand. It rises near Three Pagodas Pass (Phra Chedi Sam Ong) on the mountainous Myanmar-Thailand border and runs southeast, parallel to the border, to its confluence near Kanchanaburi town...

river in Oklahoma, U.S., rising in Le Flore county, near the Arkansas state line in the Ouachita Mountains. It flows southwest, past Pine Valley and Clayton to Antlers, where after a course of 165 miles (266 km) it turns southeast and joins the Red River...

river in central Florida, U.S., flowing between Lakes Kissimmee (north) and Okeechobee (south). It originally had a course of about 100 miles (160 km), but in the 1960s it was canalized for flood-control purposes to a 56-mile (90-km) length. The river...

river, the longest wholly within Turkey. It rises in the Kızıl Mountains (kızıl, “red”) in north-central Anatolia at an elevation of about 6,500 feet (1,980 m) and flows southwest, past the towns of Zara and Sivas. It then turns northward in a great...

river rising in Upper Klamath Lake just above Klamath Falls, Ore., U.S. It flows south for 1.25 miles (2 km) as the Link River to Lake Ewauna, where it emerges as the Klamath River, and continues generally southwesterly 250 miles (400 km) through the...

tributary of the Yukon River, in western Yukon, Canada. With its major tributary, the North Klondike, it rises in the Ogilvie Mountains and flows westward for 100 mi (160 km) to join the Yukon at Dawson, the river’s historic settlement. The Klondike...

river, east-central Tamil Nadu state, southeastern India. Formed by the northern bifurcation of the Kaveri (Cauvery) River just west of Srirangam, the Kollidam River flows in an easterly and then northeasterly direction for about 95 miles (150 km) and...